On the spectrum of two-point boundary value problems for the Dirac operator (Q1982380)

In this paper, the author studies the spectral problem for the Dirac system \[ B y' + Vy = \lambda y, \tag{1} \] where \[ y = \left ( \begin{array} {c} y_1(x) \\ y_2(x) \end{array} \right), \quad B = \left ( \begin{array} {c} 0 \quad 1 \\ -1 \quad 0 \end{array} \right), \quad V = \left ( \begin{array} {c} p(x) \quad q(x) \\ q(x) \quad -p(x) \end{array} \right), \] with the two-point boundary conditions \[ C y(0) + D y(\pi) = 0. \tag{2} \] The author establishes the existence of eigenvalues with an unbounded growth of the multiplicity for nontrivial boundary value problems of some type.